Method and Device for Regulating The Temperature Inside a Dwelling

ABSTRACT

A method and a device for regulating temperature in a dwelling having microporous walls ( 10 ) and outside thermal insulation ( 12 ) by causing outside air to flow in a wall ( 10 ) and/or between a wall ( 10 ) and its thermal insulation ( 12 ) as a function of the relative humidity of the outside air, of the relative humidity of the wall, and of the heating or cooling of the wall ( 10 ), the temperature of which is measured by means of sensors ( 30, 30 ′) mounted facing the wall and/or in the wall ( 10 ).

The invention relates to a method and a device for regulating temperature in a dwelling having walls of microporous structure and outside thermal insulation.

It is known, in particular from document FR 2 417 726 A1, to build dwellings with outside thermal insulation that leaves an intermediate space between the insulation and the walls, and to cause outside air that has been heated or cooled to flow in the intermediate space in order to heat or cool the walls, as appropriate, with the outside air being heated or cooled by heating or cooling means of conventional type, and with the walls in contact with the air acting as radiant walls for heating or cooling the inside of the building.

Nevertheless, that known technique is not very efficient and it does not enable the temperature in a dwelling to be regulated with significant energy savings.

Also known, from application PCT/FR2009/000834 in the name of the Applicant, are a method and a device for regulating temperature inside a building having outside thermal insulation and in which the walls are of microporous structure, temperature regulation being performed by measuring or estimating the temperature and the relative humidity of the outside air, and also the variations therein during day and night over the seasons, and by determining daytime and nighttime periods during which the flow of outside air in the intermediate space left between the thermal insulation and the wall serves best to cool or heat the wall as a function of requirements, while taking account of the relative humidity of the outside air and that of the air inside the building in contact with the microporous wall, and while also taking account of variations in the temperature and the humidity of the microporous wall.

That technique enables the walls of a building that constitutes a dwelling to be heated or cooled by means of a flow of outside air that has not previously passed through conventional heater or cooling means, thereby making it possible to achieve a large saving in the amount of energy needed for regulating temperature inside the building.

A particular object of the present invention is to improve that technique and to increase the energy savings it provides.

To this end, the invention provides a method of regulating the temperature in a dwelling having microporous walls and outside thermal insulation, the method being characterized in that it consists in determining the periods and the speeds at which outside air is caused to flow in a wall and/or between a wall and its thermal insulation as a function of the relative humidity of the outside air, of the relative humidity of the wall, and of temperature variations at the surface of the wall and/or inside the wall.

The invention is based on the fact that the adsorption of humidity in the form of water vapor by the microporous wall gives rise to an increase in the temperature of the wall, this adsorption continuing so long as the wall is not saturated in water vapor, it being possible for the wall to be solid or to be formed with air flow channels.

Thus, e.g. in winter, it is possible to cause cold outside air of high relative humidity to flow in the microporous wall and/or between the microporous wall and its thermal insulation, with the humidity in the air being adsorbed by the surface of the wall, thereby heating the wall, and to stop causing the air to flow when the surface temperature of the wall reaches a maximum value corresponding to its surface being saturated in water vapor, with the flow of outside air at high relative humidity being restarted in that space once the surface temperature of the wall has dropped to a minimum value, with this drop being due to the water vapor diffusing into the inside of the wall.

It is also possible, e.g. in summer, to cause hot outside air of relatively low humidity to flow in the wall and/or between the wall and its insulation, for the purpose of absorbing the water vapor contained in the microporous wall and thereby cooling the wall, with the flow of outside air being stopped once the surface temperature of the wall reaches a minimum value, and to restart the flow of low relative humidity outside air when the surface temperature of the microporous wall has risen to a maximum value, by water vapor diffusing and by heat being transferred from the inside towards the outside through the wall.

The periods during which outside air is caused to flow and those during which said flow is stopped are of different durations, e.g. a few minutes or tens of minutes for the flow periods and several hours for the non-flow periods.

According to an important characteristic of the invention, the speed of the air in the space between the wall and its outside insulation is adjusted to a low value, e.g. of the order of 0.05 meters per second (m/s), in order to heat or cool the wall by adsorption or desorption of water vapor, or to a value greater than about 0.5 m/s in order to heat or cool the wall by convection.

Thus, depending on climatic conditions, it is possible to heat or cool the microporous walls either by thermal convection by causing the outside air to flow at a relatively high speed along the walls, or by adsorption or desorption of water by causing the outside air to flow along the walls at a relatively low speed.

In a variant, for adsorption or desorption, it is possible to cause the outside air to flow at a relatively high speed in the space between the wall and its outside insulation, and to stop the flow of air when the volume of air contained in said space has been renewed, then in causing outside air to flow once more in said space after a predetermined interval of time, e.g. several tens of minutes, in order to renew the volume of air contained inside the space once more.

In this variant, the space between the wall and its outside insulation is filled with “new” outside air, the space is then closed for the length of time needed for the water in the wall or in the outside air to condense or to vaporize, and then the above-mentioned space is refilled with “new” outside air once more, and so on.

In another variant of the invention, outside air is allowed to flow freely in the above-mentioned space while limiting the speed of the air in that space to a low value, e.g. less than about 1 m/s, so as to maintain the temperature inside the building at a value that is substantially constant for a long period of time, e.g. several days or even longer.

When certain temperature and relative humidity conditions are favorable, it is possible to open the space between a wall and its outside insulation and allow the outside air to flow freely in said space by natural convection. This makes it possible to maintain a substantially constant temperature inside the dwelling for several days or several weeks, providing care is taken to limit the speed of the air in the above-mentioned space, e.g. by adjusting it to less than 1 m/s, so that temperature regulation by water vapor adsorption/desorption is predominant compared with heat exchanges by convection.

Advantageously, the method of the invention also consists in calculating the relative humidity of the outside air from its dry temperature, and from the time and the date.

The method also consists in calculating or estimating the relative humidity of the wall from the temperatures of the wall and from prior calibration.

This serves to avoid using probes for measuring relative humidity, given that such probes are extremely expensive, are of relatively short lifetime, and are very sensitive to problems of pollution that degrade their accuracy very greatly.

The invention also provides a device for regulating the temperature inside a dwelling having microporous walls and outside thermal insulation, the dwelling including outside air flow spaces provided between microporous walls and their thermal insulation, the device being characterized in that it comprises control means for controlling the flow of outside air and the flow speed of said air in said spaces, the control means receiving as inputs temperature measurements of the microporous walls in order to control the flow of outside air in the space provided between a microporous wall and its thermal insulation as a function of temperature variations of the microporous wall, of its relative humidity, and of the relative humidity of the outside air.

According to another characteristic of the invention, the device includes means for instantaneously measuring the surface temperatures of the microporous walls.

Advantageously, these means for measuring the temperatures of the microporous walls comprise infrared sensors.

Preferably, the means for measuring the temperatures of the microporous walls are mounted in the above-mentioned spaces facing the outside surfaces of the walls, in particular at the bottom and top ends of said spaces.

It is also possible to mount temperature sensor strips in holes drilled in the walls substantially across the entire thicknesses thereof in order to measure continuously the temperatures within the walls and to track variations therein. This makes it possible to control the temperature regulation device of the invention directly without it being necessary to begin by defining the relative humidity and temperature behavior characteristics of the materials of the walls.

If necessary, fans may also be provided in order to cause the outside air to flow, and outside air admission and outlet means are provided at respective vertical or horizontal ends of the above-mentioned spaces and comprise vertical or horizontal tubes, each having one longitudinal end with means for adjusting its air inlet section, e.g. a diaphragm, the tubes including air outlet orifices distributed along their length.

When the height of the space between the wall and its insulation is sufficient, the outside air may circulate therein by natural convection without it being necessary to use the above-mentioned fans.

In a particularly advantageous embodiment, the microporous walls include passages or channels for passing a flow of outside air, the walls being made up in particular of juxtaposed panels or elements, e.g. hollow bricks or the like, having air passages that are not obstructed and mutually in alignment, which passages are also in communication with the above-mentioned spaces arranged between the walls and their outside insulation, thus making it possible to greatly increase the surface area of microporous wall coming into contact with the outside air and thus very greatly increasing the performance of the invention in terms of energy savings.

In particular, the device of the invention may be combined with a controlled combined extract and input mechanical ventilation system (VMC) having top-up heater means of low power (a few kilowatts) as a function of the dimensions of the dwelling, of its geographical location, and of its exposition.

In general, the invention enables the amount of energy consumed for regulating temperature inside a dwelling to be reduced by at least 85%.

The invention can be better understood and other characteristics, details, and advantages thereof appear more clearly on reading the following description made by way of example with reference to the accompanying drawings, in which:

FIG. 1 is a fragmentary diagrammatic view in section of a dwelling of the invention;

FIG. 2 is a diagrammatic plan view of an external air admission device;

FIG. 3 is a graph plotting variations in dry temperature and in relative humidity of the outside air during a summer day;

FIGS. 4 and 5 are perspective views of hollow bricks; and

FIG. 6 is a section view on line VI-VI of FIG. 1 in a variant embodiment of the invention.

Reference is made initially to FIG. 1, which is a diagram showing a portion of a dwelling of the invention, the dwelling having outside walls 10 of microporous structure that are fitted with outside thermal insulation 12, thereby leaving spaces 14 relative to the outside face of a wall 10, within which spaces it is possible to cause outside air to flow, i.e. air taken from outside the dwelling.

By way of example, the microporous structure walls 10 are made in conventional manner using ordinary materials such as bricks, stone, concrete blocks, etc.

The thermal insulation 12 that is fitted on the outside faces of the walls 10 may be of any suitable type, and it is put into place so as to leave the spaces 14 relative to the walls 10, which spaces have a thickness of a few centimeters and preferably extend over the entire surface area of the walls 10.

Air admission means 16 and air outlet means 18 are provided at the bottom and top ends of the spaces 14, the air admission means 16 comprising for example a horizontal tube 20 that extends along the entire length of a space 14 and that is pierced by a row of orifices 22 distributed along its length, as shown in FIG. 2. One end 24 of the tube is closed while its other end is fitted with control means 26 for adjusting the air inlet section into the tube 20, the means 26 being of the circular diaphragm type, for example.

A fan 28 may be mounted on or connected to this end of the tube 20 in order to feed it with outside air through the inlet section adjustment means 26.

Similarly, the air outlet means 18 provided at the top end of the space 14 may comprise a perforated tube 20 similar to that shown in FIG. 2, one end of the tube being closed and its other end being connected to an air outlet opening.

The air outlet means 18 may be fitted with a suction fan that either replaces the fan 28 fitted to the air inlet means 16 or else reinforces the action of that fan 28.

In a variant, outside air may flow by natural convection in the space 14, the fans not being powered.

Under all circumstances, means are also provided for adjusting the flow speed of the outside air in the space 14, these means comprising for example adjustable-section diaphragms that may also be used for opening or closing the air inlets or outlets of the space 14.

At least one temperature sensor 30 is mounted in the intermediate space 14 in order to measure the temperature of the outside surface of the wall 10.

The temperature sensor 30 preferably serves to perform instantaneous temperature measurements and is advantageously of the infrared type. It is mounted on the face 32 of the thermal insulation 12 so as to face the outside surface of the wall 10.

In the embodiment shown in FIG. 1, the outside air flow space 14 has two temperature sensors 30, one at the bottom end of the space and the other at its top end, thereby enabling the temperature difference of the wall to be measured between its bottom end and its top end.

In a variant, or in addition, it is possible to fit linear temperature sensor strips 30′ in horizontal holes in the walls 10, e.g. level with the top and bottom ends of the spaces 14, these strips serving to measure temperatures and temperature variations within the thickness of the walls, these sensors preferably being of the infrared type and distributed across the thickness of the walls, being spaced apart from one another by two centimeters, for example.

The temperature sensor(s) 30, 30′ is/are connected to input(s) of a control circuit 34 that controls the inlet sections of the tubes 20 and the operation of the fans 28 in order to cause outside air to flow over the outside face of a wall 10 or several walls 10 of the dwelling as a function of the relative humidity of the outside air and as a function of the variation over time in the temperature(s) of the wall(s) 10.

The relative humidity of the outside air is not measured directly for the reasons mentioned above, given that known humidity-measurement probes are extremely expensive, sensitive to air pollution, and present a lifetime that is relatively short. It is possible to determine the relative humidity by calculation, for given time and date.

It is known that the absolute humidity of ambient air does not vary in measurable manner over the course of a day and that it varies in almost sinusoidal manner over the year around a mean value that is equal to 0.0072 kilograms (kg) of water per kg of ambient dry air with a maximum value of 0.01 kg of water per kg of ambient dry air and a minimum value equal to 0.004 kg of water per kg of ambient dry air (these values being measured in summer in the center of France).

The relative humidity of the air is given as the ratio between the vapor pressure of the air and the saturated vapor pressure at the dry temperature of the air, and it can be calculated as a function of the absolute humidity of the air, of the atmospheric pressure, and of the saturated vapor pressure by using a formula of the following type:

w·Po/(a+w)·Pvs

where w is the absolute humidity of the air, Po is the atmospheric pressure, a is a constant, and Pvs is the saturated vapor pressure, which is a known function of the dry temperature of air.

Thus, at a given time and date, it is possible to calculate the relative humidity of the air by measuring the dry temperature of the air and by using information stored in memory about seasonal variations in the absolute humidity of the air in the region where the dwelling is built.

As shown diagrammatically in FIG. 3, the relative humidity ε of the air and the dry temperature T of the air vary in opposite manner during a day, the curves in FIG. 3 being taken during a summer day during which the temperature varied between a minimum value of 15° C. at 5 AM and a maximum value of 27° C. at 3 PM with the relative humidity of the air varying from about 0.9 at 5 AM to about 0.45 around 3 PM.

By way of example, if it is assumed that the temperature of the outside air in winter is 5° C. and that its relative humidity ε is 90%, then a flow of outside air at slow speed (e.g. about 0.05 m/s) in the space 14 over the outside surface of the wall 10 will give rise to water vapor being adsorbed by the outside surface of the wall so long as said surface is not itself saturated in water vapor. This adsorption of water vapor by the surface of the wall 10 gives rise to an increase in its temperature, e.g. rising from 20° C. to 23° C., with the temperature of 23° C. being reached when the surface of the wall 10 is saturated in water vapor. The water vapor then passes along capillaries inside the wall and the heat at the surface of the wall is diffused to the inside of the wall.

When the surface temperature of the wall 10 has reached 23° C. and begins to decrease, the flow of outside air within the space 14 is stopped. The wall 10 is then observed to cool, with its heat being absorbed progressively by the inside of the dwelling. When the temperature of the wall 10 has dropped to 20° C., outside air of high humidity is caused to flow at low speed once more in the space 14 until the surface temperature of the wall rises to about 23° C.

The mean heat flux absorbed by the wall over a 15-minute (min) period of air flow has been found in one embodiment to be about 13 watts per square meter (W/m²), which corresponds to energy of about 3 watt-hours per square meter (Wh/m²). If this supply of heat is implemented three times in a day over a total wall area of about 200 square meters (m²), then the energy supplied to the building is about 2 kilowatts-hours (kWh).

It is at night when the humidity of the outside air is at its highest that outside air is caused to flow in the space 14 in order to heat the wall 10, in winter.

Conversely, in summer, when it is necessary to lower the temperature of the wall 10, outside air is caused to flow at low speed within the space 14 during high-temperature periods of the day when the relative humidity of the outside air is at its lowest. The flow of outside air over the outside surface of the wall 10 then causes water vapor to be desorbed from the surface of the wall 10, thereby lowering its temperature and thus lowering the temperature of the wall and of the inside of the dwelling.

Thus, by way of example, the outside surface of the wall 10 may go from 23° C. to 20° C. The flow of outside air in the space 14 is then stopped until the surface temperature of the wall 10 has risen to 23° C., for example, and then outside air is caused to flow once more in the space 14.

In the circumstances described above, the flow speed of outside air in the space 14 is adjusted to a value that is relatively low, e.g. of the order of a few centimeters per second (cm/s), in order to reduce the convective effect of the air flowing in the space 14, which effect opposes the transfer of heat by water vapor adsorption-desorption in the wall.

Typically, periods during which outside air is caused to flow in the space 14 have durations of a few tens of minutes, e.g. 10 min to 20 min, and they alternate with periods during which the flow is stopped that are much longer, e.g. lasting several hours (h).

It is also possible to proceed by renewing the volume of air in the space 14, i.e. by refilling this space with “new” outside air, and then closing it for a certain length of time (e.g. lying in the range 10 min or 15 min or 30 min, depending on climatic conditions), opening it and filling it once more with “new” outside air, closing it, etc. When the flow of air in the space 14 is stopped, water vapor diffuses by osmosis within the space and into the cavities in the elements forming the wall 10.

In a climate that is hot and humid, it is possible to proceed as follows in order to cool a wall 10: during the night, when the outside temperature is at a minimum temperature, e.g. about 20° C., the air is caused to flow in the space 14 at a relatively high speed, e.g. of the order of 0.5 m/s to 1 m/s, approximately. This initially gives rise to a small rise in the temperature of the wall 10 since it adsorbs water vapor, and then to cooling of the wall 10 by contact with the outside air that flows continuously over the wall. It is thus possible to lower the temperature of the wall 10 to 20° C. overnight, with this cooling sufficing to maintain an agreeable temperature inside the dwelling during the day, with the wall 10 heating up progressively until the middle of the night when it can once more be taken to a temperature of about 20° C.

This technique of heating and cooling walls 10 of a dwelling also makes it possible to keep the relative humidity of the air inside the dwelling in the range 60% to 70% approximately, which corresponds to a maximum sensation of comfort and well-being.

With the strips 30′ of temperature sensors, it is possible to measure and track the temperature variations and gradients within a wall 10 and to control the flow of outside air over the wall directly without any need to know the thermal and relative humidity characteristics of the wall.

The circuit 34 that controls the flow of outside air within the spaces 14 also controls the operation of a controlled combined extract and input mechanical ventilation system 36 that may be associated with low power top-up heater means, if necessary, or with a reversible heat pump in order to heat or cool the inside of the dwelling in complementary manner.

Simulations and measurements have made it possible to verify that the invention gives the wall 10 very great thermal inertia and great ability to regulate the temperature and the relative humidity inside the dwelling. As mentioned above, it makes it possible to reduce the energy consumed for temperature regulation in the dwelling by at least 85%.

Performance is even better in the variant embodiment of FIGS. 4 to 6.

In this variant, the microporous wall 10 is made of hollow bricks, such as the bricks 40 shown in FIG. 5, which bricks are laid in superposed and staggered rows, the bricks having parallel and rectilinear internal channels 42 that open out into the ends of the bricks and that are horizontal in the bricks 40, or vertical in the bricks 44 of FIG. 4.

In the wall 10, the channels 42 in the aligned bricks are themselves in alignment with one another so as to extend one another. Mortar jointing is provided between the rows of bricks, but not between the bricks within a given row so as to ensure that the channels in alignment can communicate with one another and also with the spaces 14 between the walls 10 and the outside insulation.

Thus, the flow of outside air between the wall 10 and its insulation 12 gives rise to a flow of outside air within the channels 42 in the bricks 40 of the wall 10, the outside air penetrating into the channels 42 and leaving those channels by being sucked through the spaces 46 left empty between juxtaposed bricks.

Provision may also be made for vertical ducts or manifolds for feeding and extracting outside air at the longitudinal ends of the wall, so as to cause the outside air to flow from one end of the wall to the other in the aligned channels 42.

Thus, the outside air, that is either dry or humid depending on circumstances, comes into contact with a surface area that is equal to the sum of the areas of the walls of the channels 42, i.e. an area that is several times greater than the vertical surface area of the wall 10 (e.g. five times greater), thereby increasing the effectiveness of the invention very considerably.

In this variant, it is possible to reduce the thickness of the space 14 between the wall 10 and its insulation 12, and even to eliminate this thickness. Under such circumstances, the outside air flows only inside the wall 10 within the channels 42, under the same conditions as those described with reference to FIGS. 1 to 3, i.e. at low speed and for a short duration, in order to yield its humidity to the wall 10, thereby heating the wall, or in order to absorb humidity from the wall 10, thereby cooling it.

The wall 10 may also be made by juxtaposing bricks 44 of FIG. 4 in which the channels 42 are vertical. Under such circumstances, the outside air flows vertically within the wall 10, and horizontal outside air feed and extract in manifolds may be provided respectively at the bottom and top ends of the wall.

In another variant embodiment of the invention, the wall 10 is made up of panels having horizontal or vertical air-flow channels, the panels being prefabricated, e.g. being made by permanent form methods.

Furthermore, the wall 10 is made of conventional microporous material (stone, bricks, concrete, . . . ) in which the microporosity may optionally be adjusted, e.g. by adding a material of the pozzolan type to concrete. 

1. A device for regulating the temperature inside a dwelling having microporous walls and outside thermal insulation, the dwelling including outside air flow spaces between the microporous walls and their thermal insulation, wherein the device comprises control means for controlling the flow of outside air and the flow speed of said air in said spaces, the control means receiving as inputs temperature measurements of the microporous walls in order to control the flow of outside air in the space between a microporous wall and its thermal insulation as a function of temperature variations of the microporous wall, of its relative humidity, and of the relative humidity of the outside air.
 2. A device according to claim 1, further comprising means for instantaneously measuring the surface temperatures of the microporous walls.
 3. A device according to claim 2, wherein the means for measuring the temperatures of the microporous walls comprise infrared sensors.
 4. A device according to claim 2, wherein the means for measuring the temperatures of the surface of the walls are mounted in the above-mentioned spaces facing the outside surfaces of the walls.
 5. A device according to preceding claim 1, wherein temperature sensor strips are mounted in holes formed in the walls substantially across the entire thickness thereof.
 6. A device according to claim 1, wherein the microporous wall includes outside air flow passages or channels communicating with the spaces formed between the microporous walls and their outside insulation.
 7. A device according to claim 6, wherein the microporous walls are made up of juxtaposed panels or elements including air passages, such as hollow bricks, the air passages of said elements being non-obstructed and in alignment from one element to a following element.
 8. A device according to claim 1, wherein the outside air flow means include fans and outside air admission and/or outlet means mounted at respective vertical or horizontal ends of the walls and comprising horizontal or vertical tubes, each having one longitudinal end with means for adjusting its air inlet section, e.g. diaphragm means, the tubes having air outlet orifices distributed along their length.
 9. A method of regulating temperature in a dwelling having microporous walls and outside thermal insulation, the dwelling having outside air flow spaces formed between the walls and their thermal insulation, wherein the method further comprising in determining the periods and the speeds during which outside air is caused to flow in an above-mentioned space between a wall and its thermal insulation as a function of the relative humidity of the outside air, of the humidity of the wall, and of temperature variations at the surface of the wall and/or inside the wall.
 10. A method according to claim 9, wherein the speed of the air in said space is adjusted to a low value, e.g. of the order of 0.05 m/s, in order to heat or cool the wall by adsorption or desorption of water vapor, or to a value greater than about 0.5 m/s in order to heat or cool the wall by convection.
 11. A method according to claim 9, further comprising in causing outside air to flow in said space and in stopping said flow of air when the volume of air contained in said space has been renewed, then in causing outside air to flow once more in said space after a predetermined interval of time, e.g. several tens of minutes, in order to renew the volume of air contained inside the space once more.
 12. A method according to claim 9, further comprising, under certain temperature and humidity conditions, in allowing outside air to flow freely in said space, while limiting the speed of the air in said space to a value of less than about 1 m/s, in order to maintain the temperature inside the dwelling at a value that is substantially constant over a long period of time, e.g. several days.
 13. A method according to claim 9, further comprising in calculating the relative humidity of the outside air from its dry temperature, from the time and the date for a given region, and in calculating or estimating the relative humidity of the wall. 